The coating of thermoplastic polymer substrates with moisture resistant barrier coating compositions to provide impermeability to gases such as oxygen, and liquids, is known. See, e.g., U.S. Pat. No. 3,282,729, which describes applying a water solution of polyvinyl alcohol (PVOH) and trimethylolphenol to a thermoplastic polymer substrate at an elevated temperature. Also, for example, U.S. Pat. No. 5,073,419 refers to a film composite comprising a linear low density polyethylene film having a PVOH coat of a thickness of about 0.1 to about 3 mils. U.S. Pat. No. 5,487,940 refers to a metallized polymeric film structure including an oxygen barrier and a moisture barrier. The oxygen barrier includes cross-linked PVOH and the moisture barrier is preferably metallized oriented polypropylene or polyethylene.
Similarly, U.S. Pat. No. 4,254,170 refers to bioriented polyester hollow bodies wherein one wall of a preform is coated with an aqueous composition consisting of at least two incompatible polymers, one of which is a water soluble PVOH and the other, a polymer latex with low water sensitivity.
U.S. Pat. No. 5,384,192 refers to a structure comprising an inorganic oxide substrate having an organic polymer layer. There is an adhesion promoting layer between the substrate and organic polymer layer. One component of the adhesion layer is poly(vinyl phenol), also known as poly(para-hydroxystyrene).
U.S. Pat. No. 5,192,620 refers to a metallized film composition comprising a polymer substrate having a surface which is modified by an adhesion promoting agent, the modified surface is provided with a skin layer of PVOH. The PVOH skin layer is applied by a solution coating process. The skin layer has a metal layer directly thereon.
U.S. Pat. No. 5,491,023 refers to a metallized film composition comprising a polymer substrate having a surface which is modified by an adhesion promoting agent, the modified surface is provided with a skin layer of PVOH. The PVOH skin layer is applied by an extrusion process. The skin layer has a metal layer directly thereon.
European Patent Application No. 0 518 646 A1 refers to polymeric article comprising a polymer film, an acidic primer layer, and a barrier coating containing a layered mineral dispersed in an acidic polymeric matrix. The polymer material of the primer layer may be intrinsically acidic or may, for example with PVOH, contain an added mineral acid, preferably sulfuric acid at a concentration of 4% to 8% by weight relative to the primer polymer.
U.S. Pat. No. 5,330,794 refers to a ceramic protective coating on a surface, wherein said coating comprises a binder (e.g., potassium polysilicate), filler (e.g. talc, dichromium trioxide, ceramic fibers or microspheres), and in some cases active ingredients.
While conventional corona treatment of polyester polymeric articles immediately prior to application of a waterborne barrier coating is sufficient to achieve a good barrier coating, it is difficult to corona treat three-dimensional objects, such as bottles, uniformly. Thus presently available methods for applying waterborne coatings to polyester articles produce coatings that are uneven and possess less than optimal properties.
There remains a need in the art for better methods and compositions for applying waterborne coatings to polyester articles.